Floyd Mayweather takes in Heat practice

Mayweather was a surprise guest at Heat practice Sunday morning, sitting courtside with team president Pat Riley, managing general partner Micky Arison and other members of the franchise's brain trust. It's rare for any outsider to get invited into Heat practice, though Mayweather's resume — unbeaten in 45 fights and generally considered the best fighter of his era — certainly earned him the ultra-VIP access.

"We're trying to defend two titles. He's been defending for a long time," Heat star LeBron James said. "He definitely knows where we're coming from. It's exciting at the end of the day to have someone, one of the greatest of all-time, to be in the presence. It's something you can talk about years from now. ... We're honored and blessed to have him in the building."

Mayweather, who left just as practice was ending, gave the Heat a brief speech, reminding the two-time defending NBA champions about the need for hard work and dedication.

He's been a courtside regular at Heat games for many years.

"From one champion to another, he just talked about him being proud of us, how we handled ourselves," Heat guard Dwyane Wade said. "He knows as a champion how hard it is to go out there every night and compete, when someone can take you down and take what you work for. He just kept telling us how proud he is of us and that'd he'd be here to support, just as he was for many years."

Boxing isn't foreign to the Heat. James and Wade have used it as a training and conditioning tool in the past, and Heat coach Erik Spoelstra — whose mother hails from the Philippines — is a longtime fan of that country's boxing superstar, Manny Pacquiao.

"Champs-to-champ respect, that's universal and pretty awesome," Spoelstra said. "Our guys are obviously in awe of what he's been able to do for an extremely long period of time, 17 years being on top. That's almost too remarkable to even fathom."

Mayweather left without talking to reporters. He posted a dominating win over Canelo Alvarez last month in the richest fight ever, one that generated nearly $150 million in revenue in TV sales alone and earned Mayweather a staggering $41.5 million payday.

Wade said being "the baddest man in the world" was enough criteria for Mayweather to get into practice.

"If you got up today and you were a little tired, you'd walk in and see the champ and work a little harder," Wade said. "So that was cool. ... Not too many people come to Miami Heat practice. It was a shock seeing him sitting up here at practice. We haven't done that in my 11 years here too much."